They only happen with certain files. I notice it when syncing to my iPod or listening to music, for example. One music file will be a DEVIL FILE and cause the system to throw the I/O errors into the log after hanging up really badly (slow UI, processes crash, etc).
If I delete that one file then no problems for a while until another DEVIL FILE shows up.
I'm trying to figure out if maybe the iTunes-LAME script I use so I can use the LAME MP3 encoder might be contributing to this, or maybe LAME itself, but I can't see how. Maybe something is messed up with 10.4.3?